The aim of this project is to study the structure, function and expression of lymphocyte cell surface glycoproteins. The long-term goal is to contribute to an understanding of immune function and hematopoietic differentiation. It is proposed to continue to study the lymphocyte cell surface by means of monoclonal antibodies using biochemical and genetic analysis. Monoclonal antibodies against the Ly-5 alloantigenic determinant of T200 glycoportein and the murine transferin receptor will be obtained and used in cell lineage studies within the hematopoietic system. Characterization of cell surface glycoproteins previously defined by monoclonal antibodies will be completed. As an approach to both delineating the early stages of T lymphocyte differentiation and overcoming some of the present limitations in studying functional aspects of the cell surface, cloned cell lines from bone marrow cultures of B6.PL-Thy-1.1 mice grown in conditioned medium (Con A sup) will be obtained and characterized. The use of such cell lines to study cellular function and differentiation in vivo and the role of specific cell surface molecules in these processes will be investigated. As a second approach of relating cell surface structures to cellular function, lectin-resistant mutants of a cloned natural killer (NK) line will be obtained to investigate the role of cell surface carbohydrate in NK acitivyt and an effort will be made to identify novel cell surface molecules restricted to the NK cell line.